PIDC Dos and Don'ts - Field Crops Edition

June 15, 2023 9:50 AM
Blog Post

We’re well into the growing season in Iowa. We are in full swing in the Plant & Insect Diagnostic Clinic (PIDC) as growers, certified crop consultants, and field agronomists start to notice problems in their fields. While there is information on our PIDC webpage ( about the services that we provide, with some sample snafus this spring, I figured it was time to write a brief blog article to remind you here, too.

At the PIDC, we accept several different sample types: plants, insects, and soil. But what can we actually do with each kind of sample, and what can’t we do? Let me lay it out for you.


Plant samples

DO send us plants for plant problem diagnoses.

DON’T send us plants for A) plant identification or B) herbicide residue testing. 

  1. If you want to get a plant identified, we recommend contacting your county office or Extension Field Agronomist for help, as they have several resources at their fingertips that they can use to help! For more on finding your local office, click here. And you can click here to find your regional Extension Field Agronomist.
  2.  If you’re concerned about herbicide drift or general damage in your field, you can read this article, and clicking here will take you to a list of laboratories that can test for herbicide residuals on plants. If you plan on sending a sample to one of the labs listed, we advise you reach out to them before submitting a sample to ensure you send all the necessary information and the right kind of sample.

DO fill out our sample submission form in its entirety (there are two pages!) and be as thorough as possible when describing the problem, including when the problem was noticed, the distribution of the problem, and much, much more. The more information we have, the easier it makes our job in the PIDC, and the faster you’ll get results. Click here to go to the download page for the plant problem diagnosis form.

DON’T send money with your sample submission form. The University will bill you after services are complete, and you get your sample report.

DO send us photos to go along with your plant problem submissions. As they say, a photo can say 1,000 words and are very helpful in understanding the problem and its distribution within the field.

Soybean field exhibiting scattered yellowing and necrosis of upper leaves
They say a picture speaks a thousand words, and nowhere is that truer than in diagnostics. Photos like this can show us the distribution of a plant problem in a much easier way than trying to describe it with words on paper. (Image credit: Daren Mueller, ISU via

DON’T use our PIDC text line to send us photos of plants or plant problems without talking to us first via email ( or phone (515-294-0581). However, photos can be sent to us via email without first talking to us.

DO consult sample preparation, packaging, and shipping guidelines on our website before sending a sample. Sample submission instructions vary by the type of plant and/or plant problem you are sending! Check out our general tips for field crops by clicking here. If you have any questions about preparing a sample, please contact us.

DON’T send a sample on a Friday, as we don’t want samples sitting in hot mail trucks over the weekend. If you send a sample on a Thursday, we recommend overnight shipping it. If you have any questions about mailing samples, ask us!

DO send us plant problem diagnosis samples while the plants are still alive. Getting an accurate identification of a plant problem or disease hinges upon having some affected and some healthy material, which represents the “zone of transition” from healthy to sick plant tissue.

DON’T send us completely dead plants and ask us what killed your crop. We are in the business of diagnosing what is killing a plant not what killed a plant. Dead plant tissue is already taken over by secondary microbes that greatly diminish our chances of identifying what killed the plant.

DO scout for plant problems all season long to avoid that moment of finding a dead patch in a field, which leaves you scrambling trying to figure out what killed those plants.

Completely mature soybean plants with black lesions on the stems and small spots on the seed pods
Season-long scouting is pivotal to avoid finding dead spots in fields late in the season that surprise you. When we receive completely dead plants, it’s often nearly impossible to determine what killed those plants. (Image credit: Chelsea Harbach).



DO send us soil for soybean cyst nematode (SCN) egg counts. For a guide on SCN sample submission, click here.  

DON’T forget to include a sample submission form with your SCN egg count sample(s). You can find the nematode submission form here.

DO use the PIDC Sample Trackers to monitor the progress of your sample once the PIDC receives it. All you need to know is your sample number and you can see where your sample falls in the nematode sample queue.

A screenshot of the PIDC Sample Tracker with instructions and two sample tracker options - plant/insect samples and nematode samples
The new PIDC sample trackers provide clients with a handy tool to track the progress of their submitted samples. This is what the landing page for the Sample Trackers looks like.

DON’T send us soil for HG Type Testing your SCN populations. If this is a service you are interested in, you can send samples to SCN Diagnostics at Mizzou or the University of Illinois Plant Clinic. Please read the information on their websites prior to sending samples.  

DO send us samples for corn vermiform complete nematode counts. The ideal time to sample for corn nematodes is between V6-V12, and the optimal sample includes corn roots. There are some plant parasitic nematodes at are what we call endoparasitic, meaning that they move around inside the roots of a plant while feeding. Including corn roots with a soil sample is a must to get the full picture of a nematode problem in a corn field. For more on sampling for vermiform nematodes, click here.

DON’T send us soil or plant samples from out of state without first calling the PIDC to give us a head’s up first.


PIDC reports

DO expect to get management recommendations (where applicable) once we are done with your sample in the PIDC. The report provides information about the diagnosis (pathogens or insects found, suspected environmental or abiotic stresses), and we research and share management recommendations, where applicable, to mitigate the problem.

DON’T hesitate to reach out to us with any questions you have!

We strive to be a top-notch diagnostic laboratory. If you have any questions or concerns, please do not hesitate to reach out to us directly at